1. Technical Field of the Invention
This invention relates to a portable mobile unit, and more particularly to a portable mobile unit suitably used to give an alarm when an uplink signal does not reach a base station even though a downlink signal can be received normally at the mobile unit.
2. Description of Related Art
In related art, a cellular phone is contrived to give an alarm (making a warning sound) when the electric wave reception condition gets too weak to keep a communication while the cellular phone is in service. This alarm is an alarm alerting deterioration of the downlink speech quality, which is raised when a stable reception and demodulation of signals is deemed to be difficult based on an electric field intensity of the received wave or an error rate of a received signal in case of a digital system.
Japanese Patent Laid-Open No. 335904/1996 discloses a portable mobile unit for detecting an abnormality-representing signal when the level of the signal transmission power increases to a predetermined reference level or more due to a fault of the portable mobile unit continues for a period of time not shorter than a predetermined reference period of time, and then raise an alarm.
In the related art an alarm concerning the communication condition of a cellular phone is a downlink speech quality deterioration alarm, however no consideration was given at all to an alarm concerning the uplink speech quality.
A portable mobile unit disclosed in Japanese Patent Laid-Open No. 335894/1996 is for detecting the abnormality ascribed to a fault of the portable mobile unit, and cannot deal with the deterioration of the line speech quality.